Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be accessed by wireless devices of multiple users sharing the available system resources (e.g., time, frequency, and power).
Generally, a wireless device may be used to transmit and receive voice and/or data communications through the wireless communication systems. One commonly used technique to increase data rates and improve antenna performance is known as spatial diversity, wherein a wireless device uses multiple spatially separated antennas to simultaneously receive and/or transmit signals on multiple wireless communications channels. Often, data is sent from a wireless device using a single transmit circuit using a primary antenna that operates in duplex with a receive circuit that uses the primary antenna, and a second receive circuit, commonly referred to as a diversity receive circuit, that uses a secondary antenna. In cdma2000 1x terminology, such a scheme for receive diversity is referred to as Mobile Receive Diversity (MRD).
The use of multiple transmit and/or receive circuits is effective in enhancing user experience through higher data transmission rates. Moreover, signals received from each of the antennas can be combined with one another in such a way as to take advantage of the fact that the different position of each antenna means that it is relatively unlikely that each antenna would be in a deep fade at the same time. Thus, the probability of having reduced wireless performance due to moving into a location of a deep fade can be dramatically reduced.
For many devices today, when the wireless device initially powers up, or when the wireless device returns from being in a mode referred to as an out of service (OOS) mode, the wireless device may only use one receive circuit coupled to one antenna to attempt to acquire a system and establish communications with the cellular network. In wireless devices having more than one receive circuit, and configured to enable MRD, if each of the receive circuits is utilized to attempt to acquire the system, the probability of acquisition may be increased. However, there are certain costs to achieving the improved probability of acquisition, such as an increase in power consumption resulting from the use of an additional receive circuit(s), as well as possible increased latency in the acquisition. Thus, there remains a need to intelligently invoke MRD during system acquisition.